Snap acting mechanism



Nov. 17, 1953 I w. A. MARTIN 2,659,238

SNAP ACTING MECHANISM Filed Oct. 1 5, 1949 Patented Nov. 1 7, 1953 mesneassignments, to Minneapolis lioneywell Regulator Company, Minneapolis;Minn., a corporation of Delaware Application October 15, 1949, Serialso. 121,59'7

(Cl. tea-100) 13 Claims. 1

This invention relates to a snap acting device and more particularly toa snap acting switch.

An important object of the invention is the provision of a snap actingdevice comprising a minimum number of parts and easily adjusted so as toprovide a precision type switch at a minimum cost.

Another object of the invention is the provision of a snap acting deviceof the above character having a novel construction wherein the pretraveland the overtravel movements may be inade to vary between wide limits bysimple and inexpensive changes.

Another object of the invention is the provision of a snap acting deviceof the above character having novel means for mounting the spring systemwherein the device may be readily changed from a manually reset typespring systern to a self-return type and vice versa by simpleadjustments.

Another object of the invention is the provision of a snap acting deviceof the above character that is positive in its action and that is of arelatively simple construction. V V 7 Other objects and advantages ofthe invention will become apparent from the following detaileddescription taken in connection with the accom= panying drawings, inwhich- Figure 1 is a side elevational view of a reset type switchembodying the present invention and showing the movable contact inengagement with one of the fixed contacts;

Fig. 2 is a plan view of the switch shown in Figure 1;

Fig. 3 is an end View of the switch shown in Fig. 2;

Fig. 4 is a sectional view taken substantially along the line 44 of Fig.2 showing the relation of the parts with an actuating force applied tothe spring system;

Fig. 5 is a side elevation view similar to Figure 1 showing the movablecontact in engagement with the other fixed contact, and

Fig. 6 shows the invention embodied in a selfreturn spring system.

Referring now to the drawings, the invention is shown embodied in a snapacting switch. In general the latter includes a base or support II, aspring system 12 mounted on the base II and having an end [3 movablebetween opposed positions with a. snap action. The base II in theembodiment shown is in the form of a generally rectangular base formedfrom any suitable insulatingmaterial.

The i g y em 12 inc udes spaced resilient 2 tension members it and aresilient compression member [7,. At one of their ends the tensionmembers It are interconnected with one end of the compression member I!to form the free end I 3. The latter is, in the embodiment shown, shapedto carry a mobile contact l5 movable between spaced stationary contactsor stops l8 and I9 defining the op osed positions between which the freeend l3 moves. As best seen in Fig. 4 the contact I 8 is formed by a headof a rivet 2| extending through the base II and interconnetd with aterminal 22. The terminal 22 carries a screw 23 for securing electriclead wires of an external circuit to the terminal. The contact l9isformed by a Z-shaped element 26 as shown in Fig. 3 having a mountingportion 21 secured to the base I I as by a rivet 28 or the like and aportion, defining the contact is, held in spaced relation to the contactl8 by a bridging portion 29., The ri'vet 28 extends through the base IIand is connected with a terminal 3| on the opposite sideoi the basewhich likewise carhes a screw 32 threadably mounted on the terininal forsecuring electric lead wires of an external circuit to the terminal 3 l7 At itsouter end 34, the mounting portion 21 is inclined at an angleand isjshapedltobe received in an aperture 36 formed in the base topositively hold the jz-sna' ed member in fixed relation on the base I l.h

The opposite end of the compression member I! is supported ina pivotalrecess 31 formed on a leg 39 or a bracket 38. The latter may be in theform of an inverted U-shaped member having spaced legs 39 and 4!. Thebracket is mounted on the base ll by a pad 43 integral with the lowerend of the leg 4| and inclined at an angle thereto as shown in Fig. 4.The pad 43 is shaped to be attached to the base I I by a rivet 44passing through the pad, the base and a terminal 46 on the OIYUOSitQSide of the base. A Screw 41 is carried by the terminal 46 forconnecting the terininal withth wii'e of an external circuit. Preferablythe bracket 38 is formed from material whichpos'itively maintains aore-adjusted shape but which may be manually deformed to vary theposition of the recess 3! for a purpose presently to appear.

A resilient tang 45 in spaced relation with the opposite end of thecompression member I1 interconnects the ends of the tension members Itopposite the end carrying the contact I5. The forward edge or the ang eis shaped to be received a pivotal recess, 48 formed in the outwardlydisposed suriace of the leg 4| of the bracket 38 and the rearward edgeextends outwardly from the recess. In this instance the pivotal recess48 and the pivotal recess 31 are disposed in a plane passing between thestops l8 and IS. The length of the tang #35 may vary, depending upon theparticular application for which the device is being used as will beapparent hereinafter.

Figure 1 shows the components of the spring system in one of its normalpositions; that is, the movable contact l5 engages the fixed contact l9and the spring system 12 is biased so that the resultant force of thecompression and tension members urges the contact l5 into positiveengagement with the contact I9. To actuate the switch shown in Figure la force is applied at some point A on the bottom of the tang 45. Asforce is applied at point A, the free end of the tang moves. In somoving the forces in the spring system are such that the tang 45 and thetension members 15 flex and store energy. Thus with sufiicient forceapplied at the point A portions of the tension members 16 are carried orflexed downwardly across the pivotal groove or recess 31 for the end ofthe compression member 11. As soon as the tension members pass thepivotal support for the compression members the stored energy in thetension member and the tang is operative to move the contact l5 betweenthe contacts l9 and i8 with a very rapid motion. In other words when thetension members it are flexed downwardly moving the tension centerlineacross the compression centerline or through the axis of maximum stress,the movable contact [5 moves from the contact 19 into engagement withthe contact IS with a snap action and the resultant force of thecompression and tension members is reversed. The relative position ofthe parts at the instant of actuation of the spring system is shown inFig. 4.

Fig. 5 shows the relation of the parts after the movement of the contactl5 from engagement with the contact 19 into engagement with the contactl8. The tension members iii are disposed below the pivotal recess 3']for the compression member I! and the contact [5 is positively urgedinto engagement with the contact 18. The actuating force has beenremoved from the tang 45 and the latter and the tension members tend toassume a position in which they are coplanar. Where desired the tang 45may be initially inclined at an angle with respect to the plane of thetension member it. In the latter case when the force A is removed,tension members l6 and the tang 45 will assume their initial position.

The operation of the switch in the reverse direction in which thecontact 15 moves from engagement with the contact 18 into engagementwith the contact I9, is substantially the same as that described aboveexcept that the force is applied to the top of the tang 45 and themovements are made in the reverse direction to that described above.

From the above it is apparent that the point A at which the operatingpressure is applied to the tang may be at any position from a pointadjacent the pivotal recess 48 to the extreme outer end of the tang. Itwill also be apparent that less movement of the member, applying theforce to the tang, is required to efiect actuation of the snap springsystem when the point A is adjacent the pivotal recess 48 than when thepoint A is adjacent the end of the tang. It is therefore apparent thatthis construction can be used for applications having widely varyingpretravel movements. It should also be noted as the distance between thepivotal recess 48 and the point of application of the actuating forceincreases the force required to actuate the spring system decreases.

As soon as the spring system is actuated; that is, as soon as the tang45 has been moved a sumcient distance to effect actuation of the springsystem any additional movement 01' the tang 45 thereafter is overtravelmovement. The resiliency of the tang 45 permits considerable overtravelmovement depending on how far the point A at which force is applied isfrom the pivotal recess 48. Thus, this switch may be used inapplications where the overtravel movement varies over wide ranges. Themovement differential also increases as the point of application offorce is moved outwardly from the pivotal recess 58. Because theoperating characteristics of this switch change considerably dependingon the location of the point A, it is evident that this spring systemhas many applications and can be operated by widely varying forces.

In Fig. 6 there is shown another embodiment of the invention. Thisembodiment of the invention differs from the construction shown in Figs.1-5 in that the pivotal recess in a bracket 55 for supporting the end ofthe compression member 55 and the pivotal recess 59 supporting the tang6i lie in a plane passing below the contact carrying end of the springin all positions thereof. In other words, in Fig. 6 the arrangement ofthe pivotal recess 54 is such as to provide a self-return spring. Thedotted line showing of the spring system in Fig. 6 illustrates theposition of tang 6i when displaced upwardly by the operating force tourge the mobile contact against the lower stationary contact 58. In thefull line position of Fig. 6 the spring system 42 is in a momentaryposition of unstable equilibrium immediately after the upward operatingforce on tang 6| has been removed and just before the mobile contact I 6returns under the selfreturn action of the spring system to its normalposition in engagement with upper stationary contact 57.

The above described constructions are simple. The component parts may beformed as stampings. Thus, the tension members, the compression memberand the tang may be formed as a single metal stamping from suitableresilient material. This construction is easy to assemble, disassembleand service.

I claim:

1. In a snap acting device, the combination of opposed stops, spacedresilient tension members interconnected at one end to form an end freeto move between said stops with a snap action, a compression memberhaving one end connected with said free end, means for pivotallysupporting the opposite end of the compression member, a tang pivotallysupported in fixed spaced relation to the pivotal support for thecompression member to form a snap spring system having an axis ofmaximum stress, said tang interconnecting the opposite end of thetension members and being movable between opposed positions, movement ofthe tang between said positions effecting storage of energy in thetension members and flexing them through the axis of maximum stress tomove said free end between said stops with a snap action.

2. In a snap acting device, the combination of spaced tension membersinterconnected at one end to form an end free to move between opposedpositions, a compression member interconnected at one end with said freeend, means sister the opposite end-of the compressed er an elongatedtang inteionnecting opposite ends of the tension members dextending in adirection away from the compression member, and fixe'd' means sup ortngsaid tang in: spaced r eiationto said support for said compressionmember to stress said tension ai-iiicoin-'- press'iolri members todefine a; snap Spring system havin an axis or maximum stress, said tangbeing movable to move the tension members to move the tensioncenterl'ine through the axis of maximum stress to actuate the snapspringsystem.-

3; In asnap acting device, the combination or. a base, spaced stopsmounted on said base;

an inverted u shaped bracket mounted on said base in spacedr'el'atioiito said stops comprising spaced legs and a bridging portioninterconnecting said legs, each of said legs having a recess formed onits outer facing surface, a-c'ompression member having an end free tomove between limits defined by said stops with a snap action and an endpivotally'rec'eived in one of said recesses; spaced tension membersdisposed on opposite sides of said bracket and movable between opposedpositions, one end of said tension members being interconnected withsaid free end of the compression member, and an elongated resilient tanginterconnecting the opposite end of the tension members and pivotallyreceived in the other recess to stress the tension members andcompression members to define a snap spring system having an axis ofmaximum stress, said tang being movable about its pivotal mounting tostore energy in itself and the tension members to move the tensioncenterline about a fixed point and through the axis of maximum stress toactuate the spring system with a snap motion.

4. In a snap acting device, the combination of a base, opposed stops, abracket including spaced legs and a bridging portion interconnectin saidlegs, each of said legs having a recess formed on its outer facingsurface, and one of said legs having a pad in side by side relation withthe base for securing the bracket thereon, a compression member havingan end free to move between said stops and an end pivotally received inone of said recesses, spaced tension members disposed on opposite sidesof said bracket and movable between opposed positions, said tensionmembers being interconnected with said free end of the compressionmember, and an elongated resilient tang interconnected at an endadjacent the compression member with the opposite end of the tensionmembers and pivotally received thereat in the other recess to stresssaid tension and compression members to have a resultant force urgingsaid free end into engagement with one of said stops, said tang beingmovable about its pivotal mounting to move the tension members to effecta reversal of said resultant force acting on said free end to move thelatter out of engagement with one stop into engagement with the otherwith a snap action.

5. The combination recited in claim 3 in which said recesses aredisposed in a plane passing between the limits.

6. The combination recited in claim 3 in which said recesses aredisposed in a plane passing to one side of the free end.

7. In a snap acting device, the combination of a base, spaced stops, abracket having recesses on opposite sides thereof, a compression memberhaving an end free to move between said stops with a snap action and anend pivotally received 6 n said recesses,aresnrmt tensioamenser ansbetweenepposd'pesitiensanilin ticonneetd with 'said resend-' 0s the mpies= 'sitm member, a resilient tang connected to the opposite end of thetension member and pivotauv supported the other recess on said bracketfi xed spaced relation from tli pivetaI mount-'- for the compr ssionmember to stress we ceznp'*'ssion anatensien members to define asnap-spring system ha' gan axis of maximum stressgsai a tang being"movable about its pivotal to in vs the tens-ion stress line through th 1a isof maximum stress and storing energy the tensionmember to actuatethe spring system. 7 V g 8. The ombmatibh i'ecited in: claim 7 in whichthe braeket "is manually deformable to permit inov'ing'che er thepivotal recesses with respect to-the other: M r 9*. In asnap actingdevice, the combination or spaced stops, spaced resilient tensionmembers interconnected at one end to form an end free to move betweensaid stops, a compression mem ber interconnectedatone end with said fieeend, means supporting the opposite end of the com pression member, anelongated resilient tang interconnecting the opposite ends of thetension members, and means pivotally supporting said ,tangin fixedspaced relation to said support for ,said compression member to stresssaid tension and compression members to define a snap spring systemhaving an axis of maximum stress, said tang being movable in onedirection in response to the application of a force thereto to flex thetension members in the opposite direction to move the tension stressline about said fixed ipivotal means through the axis of maximum stressto move the free end between said opposed stops with a snap action.

10. In a snap acting device, the combination of opposed stops, spacedtension members interconnected at one end to form an end free to movebetween said stops, a compression member connected at one end with saidfree end, means for supporting the opposite end of the compressionmember, a normally unstressed resilient tang interconnecting oppositeends of the tension members, and means supporting said tang in fixedspaced relation to said support for said compression member to stresssaid tension and compression member to have a resultant force urgingsaid free end into engagement with one of said stops, said tan beingmovable to move the tension members to efiect a reversal of saidresultant force acting on said free end to move the latter out ofengagement with said one stop into engagement with the other stop with asnapaction.

11. In a snap acting device, the combination of opposed stops, aresilient tension member and a compression member interconnected at oneend to form an end free to move between said stops with a snap action,means for pivotally supporting the opposite end of the compressionmember, a tang connected to the opposite end of the tension member andpivotally supported in fixed spaced relation to the pivotal support forthe compression member to form a snap spring system having an axis ofmaximum stress, said tang being movable between opposed positions,movement of the tank between said positions effecting storage of energyin the tension member and flexing the tension member through the axis ofmaximum stress to move said free end between said stops with a snapaction.

12. In-a snap acting device, the combination of opposed stops, aresilient tension member and a compression member interconnected at oneend to form an end free to move between said stops with a snap action,means for supporting the opposite end of the compression member, aresilient elongated tang connected to the opposite end of the tensionmember and pivotally supported thereat in spaced relation to the supportfor the compression member to form a snap spring system having an axisof maximum stress, said tang extending away from its pivotal support ina direction away from the free end of the tension and compressionmembers and being movable between opposed positions, movement of thetang between said positions effecting storage of energy in the tang andin the tension member and flexing the tension member through the axis ofmaximum stress to move said free end between said stops with a snapaction.

13. In a snap acting device, the combination of spaced stops, a tensionmember having an end free to move between said stops with a snap action,a compression member having one end connected with said free end, meansfor supporting the opposite end of the compression member, one of saidmembers being resilient, an elongated resilient tang in spaced relationto the said one end of the compression member connected to the free endof the tension member, said tang being movable between opposedpositions, and means for supporting the tang adjacent its connection tothe tension member to form a snap spring system having an axis ofmaximum stress whereby movement of the tang between said positions movesthe tension member around the means supporting the tang through the axisof maximum stress to move said free end from one stop into engagementwith the other with a snap action.

WILBER'I' A. MARTIN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,295,463 Fetter Sept. 8, 1942 2,429,813 Hausler Oct. 28,194'!

